Document 856ejD1noKDQ0n4vR59BgjokZ

E. I. DU PONT DE NEMOURS & COMPANY PIGMENTS DEPARTMENT 256 VANDERPOOL STREET NEWARK, NEW JERSEY Copy No. / CN NEWARK PLANT PIGMENT COLOR RESEARCH REPORT \ Final Report ELECTRON DIFFRACTION STUDIES PART II - APPLICATIONS Period Covered: JUNE 1944 - APRIL 1945 FILE: DATE: 145 <,2 1 "14*47 \ NJ9S0 N41559 Serial Ho. KN-46-89 Copy Bo. / Copy tot #1 - Numerical File 2 - Research Office (145.2) 3 - Library Rile (148.8) 4 - Imperial Chemical Industries. Ltd. g- g . w n 7 * Physics Laboratory 8 - W. F, Spfengeman 9 - A. W. Kenney, Experimental Station, Wilmington 10 - Extra 11 - * NEWARK PLANT PIGMENT COLOR RESEARCH REPORT Final Report Titles ELECTRON DIFFRACTION STUDIES PART II - APPLICATIONS Period Covered: JUNE 1944 - APRIL 1945 SUBMITTED BY: F. KARUSH APPROVED BY: Mb . H. PERKINS- ^ DATE SUBMITTED: 1-2-47 DATE ISSUED: 1*14-47 ______ N41559.01 DUP050150644 -8 morxjpTiai This report presents a description of the application of the electron diffraction camera to pigment problems. The camera Itself is described in Pert I, KS-46-76, which also includes the pro* oedure for the preparation of diffraction mounts and for the measure* amt of the diffraction patterns* In the work presented here the attempt was made to apply the diffraction technique to various types of pigments* While this technique is particularly suitable for studying thin surface films, its utility in the identification of the crystal structure of pigments mas also investigated* This appeared desirable because some pigments have a particle else small enough to yield satisfactory patterns* Furthermore, in some cases the particle sice may be even too small to yield a useful x-ray diffraction pattern and yet may give an excellent electron diffraction pattern* 1* Medium (FbCrOg) and light yellows (IfeGrOg & ffeSK^} yield satisfactory electron diffraction patterns. All patterns of samples of these pigments are usually identical and agree satis factorily with the x-ray diffraction pattern of aonoolinic lead chromate with respect to the values of the interplanar spaoings. However, significant differences in relative intensities between the x-ray and electron diffraction patterns are observed* This can be largely attributed to the effect of the orientation of the needleshaped particles in the electron diffraction mount* If a more symmetrically shaped chroma yellow is used, a pattern is obtained Which shows the same ring diameters as the usual electron diffraction pattern but considerably different relative intensities* 8* The eleotron diffraction method is not suitable for the study of the .phase composit ion of such systems as FbOrQs - FbSOg and FbOrua * Fbs (PO4)|U The patterns are often of poor quality and like that of FbCrOg are quite complicated. X-ray diffraction Is a much more satisfactory method for this purpose. 3* Treatment of lead chromate with as little as T& sodium stearate gives rise to a new set of rings in the diffraction pattern together with some faint rings from the FbCrCty pattern. This means that it is possible to deteot and study mono-molecular layers of long chain compounds on FbCrOg and probably other pigments* 4* Electron diffraction does not afford positive evidence for the coating of FbGrO* with aluminum hydrate, probably because the latter is amorphous and does not give rise to distinctive rings in the diffraction pattern. DUP050150645 5. All iron blues examined, including B-57-D, B-6B-D, B-197-2) and B-216-D, gave identical electron diffraction patterns, showing that they have the same crystal structure* Because of the excellent quality of the iron blue pattern and the symmetry of the iron blue structure {face-centered cubic, length of cube 10*2 angstroms), it is used to determine the instrumental constant of tie diffraction camera* This constant permits the easy conversion from ring diameters to interplanar spaoinga* Attempts to detect the presence of adsorbed layers of stearate and Fixanol cm iron blue have been unsuccessful* This is probably due either to the original absence of suoh layers or their ready removal in the course of preparing the diffraction mount* 6* Electron diffraction patterns of msifl^iee of barium llthole and duols show at most some variation of relative Intensities but a constancy of the ring diameters* This means that duolieation does not involve a crystal structural change of this pigment* 7* A series of samples, prepared by diaaotlzlng mid coupling Bed SB Acid {o-chior-p**toluidine-iB-sulfonic acid) with beta naphthol and precipitating with strontium and calcium In various ratios, showed almost identical patterns* Substitution of one metal by the other apparently leaves the structure unchanged* A typical pattern is shown In Fig* 4D* 3* The study of coalesced phthaloeyaninee including BX-CR (TiOo + CPC) did not lead to any unequivocal results* Only in the ease of phthaloeyanine coalesced with sine oxide did the diffraction pattern indicate coating of the oxide by the colored pig ment* 9. Samples of hake Red S (p-toluldine-m-sulfonic acid BOB, Ba, roslnated) made with use of either bicarbonate, soda ash or alkali gave diffraction patterns which showed that the samples possessed identloal crystal structures* Pattern A of Fig* 6 is typical of these* 10* The electron diffraction method often can be used to distinguish and identify structurally similar organic yellow pigments* Identity of diffraction patterns does not, however, always mean identity of composition as Illustrated by the fact that diofalorbenzidine diazofclzed and coupled to aeetoaeetanllide gives a compound with a pattern identloal to that from the compound obtained by coupling with acetoacet-metaxylidide. 11* It is clear from the results of this study that in many cases the electron diffraction technique can yield information, otherwise unavailable, which may be useful in the solution of specific pigment problems. The possible utility of this technique depends upon the particular problem under consideration and must be evaluated for each DUP050150646 case* Because the electron diffraction method is particularly suit able for studying surface films, it appears desirable to continue the exploratory Investigation of adsorbed layers on pigment particles with this method* mJWMCT OF EKFERIMBHTAL DETAILS Unless otherwise noted the diffraction patterns presented here have been obtained using 40 kilovolt, electrons* The prints exhibited in this report represent 2-fold magnifications of the original patterns* The exposure time for each print has been varied for the various groups of rings to make visible all the rings which can be seen in the negative* Thus the actual relative Intensities are not faithfully reproduced In the prints* A* Chrome Yellows Medium and light yellows belong to the raonoolinic system and ore usually needleshaped* A typical pattern for this group is given in B of Fig* 1* This is the pattern of a light yellow (Y-2034, lot 7645) m electron micrograph of which is shown in Fig, 2, B* The uniqueness of this pattern depends to a large extent on the Shape of the pigment particles* If another pigment of identical composition but of different shape is used, shorn In Fig, 2, A, a pattern quite different in appearanee is obtained* This pattern Is shown in Fig* 1, A and actually differs from B only in the relative intensities of the rings* This difference arises from the fact that asymmetric particles assume a preferred orientation when mounted for electron diffraction or electron microscopy. This is evident from Fig. 2, B where practically all the needles lie in the plane of the paper. The orientation of crystals in a diffraction mount can also be detected by changing the angle of incidence between the electron beam mod the film supporting the pigment particles from 90 to another angle, *g* 4SW* This was done in the case of a sample of lead chromate and the pattern obtained Is shown in Fig* 1, C* It is seen that instead of continuous rings two or mors arcs appear, thus furnishing unequivocal evidence of preferred orienta tion* In Table I is given a comparison of the electron diffraction data from the pattern of Pig* 2, A with x-ray diffractlean data of monoclinic lead chromate* It is seen that there is satisfactory agreement with respect to the values for the interplanar spaoings. However, significant differences exist in the values iStitb relative intensities. To what extent this can be attributed to orientation effects is not known* An effort was mad to determine if the electron diffraction technique could be used to study the phase composition of the systems PbGr04 - FbSO^ and PbCrO^ - Pb3tP04)g, as well as to observe any surface effect in these mixtures. Pb3(P04)2 gives a fairly satisfactory pattern, shown in Fig, 3,A but that of PbS04 is quite poor. The pattern in DUP050150647 Fig* 3. B is that of a sample containing 40# PbOrOA and 60# fbgtPQ^g* copreolpitated. It illustrates the complicated patterns obtained from ouch mixtures and indicates the excessive difficulty in attempting to make quantitative estimates of phase composition* Pot* purposes of comparison, a pattern of momoolinic FbOiH^ is shown in Fig* 3, c* It is quite clear that this technique is unsuitable for studying the above systems* Samples of ffeOpCSU containing up to IS# aluminum hydrate sere examined but unequivocal evidence for tbs presence of the hydrate cm the pigment surface could not be found* One rtasoa for this is probably that the hydrate is amorphous and consequently dees not give rise to way distinctive rings* with samples of FbCrO* which had been treated' with aluminum hydrate and boiled, a alight bm definite change in the relative intensities of the rings of the Pb0r04 pattern was observed* fhe precise significance of this result has not been established* Studies with stearate-ferabed FbCrO> gave very encouraging results with reapeob to the study of organic surface treatments* it was found* for example* that a sample of Fbdpdfg treated with as little as 1% of sodium stearate ha the slurry gave rise to a new set of ' strong rings with the fhOrO* rings only faintly apparent* k pattern of suoh a sample (969-36B) Is shorn in Fig* 3* D and is to be compared with the pattern of untreated IbGrOg Just above it* On the assumption that the long stearate chain is oriented perpendicularly to the crystal face and the specific surface of the FbCrO* Is 5 square meters per gram* it can be calculated that a monomolecular layer of stearate requires approximately 1# of sodium stearate* It seems very likely that suoh a moaomoleoular layer is responsible for the new rings end greatly reduces the diffraction by the FbCrOa* The use of 2*3# sodium stearate gives about the same pattern. The data from such a pattern (223o) are given in Table II which lists the ring diameters* eorresponding interplanar spacings si&, relative intensities and the Identifier cation of the rings in terms of FbGrOg or stearate* KeebasicaX mixtures of FbCrO^ and either sodium stearate or lead Stearate were used as controls* With as much as 3-1/2# of stearate the patterns of these controls were essentid ly equivalent to that of FbGrO*, with indication of the strongest ring of the Fb stearate pattern* The pattern obtained from Fb stearate Itself is the same as the set of new rings appearing in stearate treated FbCr04* The choice of the medium in which the sample is dispersed is very important with respect to the appearance of the stearate rings in treated PfeOrOa* Amyl acetate is satisfactory in this res pect but when mixed with butyl or methyl alcohol the stearate rings are hardly apparent* Ethyl acetate is also objectionable on this account as is also the presence of even a slight amount of nitro cellulose in the dispersion* DUP050150648 -6- b. ^ 01 all the pigments studio#. iron blues yield by far the bests electron diffraction patterns* This is because of their mall particle else, making them transparent to electrons, and their highly symmetrical strueMwre (face-centered cubic) . A typical Iron blue pattern is shewn In Fig* 4, A and is given by all iron blue pigments examined, including B-S7-D, B-66-D, B-187-D and B-816-D* Since the lattice constant of iron blue is accurately known, 10,2 Angstroms, this pattern con be used to obtain the calibration constant for the apparatus* This constant is used to convert ring diameters into intarplanar spaatags, The data involved in the calculation of this constant are included in Table III which lists 28 ring diameters, their relative intensities and the corresponding values of h, k, 1 and the intarplanar apacings. Satisfactory iron blue patterns can be obtained with 20 KV electrons* Attempts were made to detect the presence of surface coat ings on iron blue samples treated with sodium stearate or Fixsapl. Even when as mush as 30% of one of these agents was used no evidence of an adsorbed organic layer was observed. The slight addition to the pattern was what might be expected from a mechanical mixture. It is still unknown whether these agents were not originally adsorbed by the pigment or whether they were removed from the surface in the course of the mounting procedure* In this connection it should be mentioned that ethyl acetate was used as the dispersion medium. In view of f$f behavior with stearate treated PbCr04 it Is not unlikely that this solvent would remove an adsorbed film of stearate or Ftxanol, C, The "Duol" Effect The effect of rosin on a barium lithol (2-naphthylamine sulfonic acid * BS, Ba) was investigated by the electron diffraction technique. Samples <1127-22 series} which contained varying amounts of rosin up to 186 grams per mole of color (mol* wt* 515*4), and sub jected to temperature treatments ranging from room temperature to boiling for awe than one hour,were studied* The only change observed occurred with a sample containing 11 grams of rosin per mole of color which had been boiled for 2 to 4 minutes* The pattern of this sample is shown In Fig, 4, C and is to be compared to B in Fig, 4, The latter la the pattern obtained from lower temperature samples of the same rosin content. Curiously enough, it is also the pattern found with all samples with less than 11 grams of rosin as well as more rosin, regard less of the heat treatment. Close examination reveals that pasterns B and C of Fig, 4 differ only ha relative intensities. It seems unlikely, therefore, that duolisatlora involves any crystal structural change of the odor. It may be added that barium rosinate Itself gives no diffrac tion rings. D. Organic Yellows The possibility of the identification of structurally similar organic pigments was investigated by a study of the diffraction patterns of a series of organic yellow toners. Good examples of such DUP050150649 patterns are shorn in Pig* S, B and C* B is the pattern of a com petitive pigment {0#47936) and is Identical with th pattern ob tained fro the product prepared by coupling diahlorbeagidine with, acetcreet-reta-jsylidide A very interesting series of patterns la obtained fro the yellows prepared by coupling diobloxbenzidina with aeetoacefcanlltde* aoetoaoet-meba-xylIdldo, aoefcoaoet*SCBS-aHs0~ anilide; and aceto&oetS*S(CBgO)g-smili&e respectively* The patterns of these substances are show in Pig* 6, A, B* C and 0 respectively* She Introduction of two aethyl groups Into aoetoaoetanilide apparently leaves the crystal structure unaltered as a comparison of patteres A and B indicates* However* if one methyl group and one aetboxy group are introduce^ a definite ohang in structure results* as seen in pattern C* The nm of two ajethosy groups does not lead to any further & feeratlon of structure as indicated by the identity of patterns 0 and la the case of para-ohlor-ortho-nitro-anilin coupled to aoetoaeatanilide* aoefcoaoet-ortho-toluldide and aoctoacat-meta-xylldide respectively* the crystal structure is more sensitive to substitution in the scored component than it is in the case of the diofalorbensidin aeries* This is clear fro the fact that the pattern of these three producta, shown In Pig* 7* Bt C and B* differ from one another* A pattern of the standard Hansa Yellow toner* YT-446-D (nets-nitro-paratoluidine -* aoetoaoetenillde) Is given in Pig* 7* A* DUP050150650 TABLE I. Ooaparleon of electron diffraction data (2SSB) and x-ray diffraction data for monoollnic FbCrO^. X-ray data from lad. & Eng. Chem*10.489(1938) Ring dlam. In <m* ELECTRON PIPFRACTIOX X-RAY Intorplanar Ihterplanar .p.0^ in Relative .P^ln Relative Isvtemltv infcenalfcv 0.89 um 1.20 1.36 1.48 1*64 1*76 i.n 1.98 8,24 8*40 2,77 2*87 3.02 3.19 3.29 3.35 3.45 3.61 3.30 3*95 4*12 4.45 4.96 4.34 3.69 3*23 8.99 2.70 2.33 2*32 2.83 1*97 1*34 1*60 1*34 1*48 1*39 1*34 1*32 1.28 1*22 1.16 1.1ft 1.07 1.00 0.20 0*27 0.20 0.70 1.00 0.34 0.35 0*27 0.27 0.45 0*43 0.87 0.20 0.20 0*27 0.20 0*20 0*27 0.8 0.80 0*20 0.20 0,80 4.97 4*36 3.73 3*26 3*91 8.71 2*33 2*32 2*25 1*97 1*35 1*81 1.54 1.42 * * ** w* * 0*23 0.46 0.11 1*00 0*86 0*11 0.11 on 0.34 0.40 0.34 0.06 0*06 0*09 * m ** ** mm m a* DUP050150651 *9* MMIJBU Electron diffraction data team pattern of FbOrO, treated with 2*1/2% Ka stearate(pattern no* 2230*) Ring Ho* 1 2 3 4 5 6 7 a 9 10 U 12 IS 14 IS Ring diameter ..... JfLJS*_____ 0,07 1.06 1.20 1*34 1.45 1,77 1.94 2,02 2,14 2,22 2,30 2*65 2.74 2*83 3.08 Ifcterplanar spacing in mmtrom. 5.08 4.16 3*63 3.30 3.05 2.50 2.28 2.19 2.06 1.99 1,36 Relative Intensity 0*22 1.00 0.70 0*22 0*46 0*37 0*22 0*28 0,16 0.16 1,67 1.614 1.563 1.435 0*16 0.16 0*16 0.16 Identification FbCr04 Stearate Stearate Rcr04 FbCrQ4 Stearate PbCr04 Stearate Stearate PbCr04 Stearate PbCr04 PbGr04 PtCr04 PbCr04 J%Cr04 DUP050150652 -10TABLB III. Calculation of conversion oonatant from diffraction pattern of Iron blue (1S1C.) K Phki a ao 10.2A later- Goaver- planar siea am* King Ho. Ring diam* la eat, 0. Relative intensity hR 1 h2+kS+l2 iSfz&zp liSaasfa stant, K la eat#, A 1 0.76 2 0.86 3 1*22 4 1.43 $ 1*60 6 1.72 7 1.93 8 2.12 8 2.46 10 2.69 11 2.78 12 2.88 13 3.01 14 3.12 IS 3.23 18 3.57 17 3.68 18 3.77 19 3.88 20 4.06 21 4.32 22 4.41 23 4.80 24 4.67 25 4.73 28 4.98 27 5.07 28 5.30 0.24 111 3 1,732 0,60 200 4 2.000 1.00 220 8 2.828 0.14 311 11 3.317 0.60 222 12 3,464 0.72 400 16 4.000 0.86 420 20 4.472 0.19 422 24 4.899 0.78 440 32 6.667 0.60 600 36 8.000 442 0.72 620 40 6.325 0.14 622 44 6.633 0.19 444 48 6.928 0.72 640 32 7.211 0.60 642 56 7.483 0.50 820 68 8.246 644 0.30 822 72 8.485 880 0.24 662 76 8.718 0.24 840 80 8,944 0.40 0.24 664 88 9.381 860 100 10.000 1000 0.40 862 104 10.20 1020 0.24 666 108 10.39 1022 0.40 864 116 10.77 1040 0.24 1042 180 10.93 0.19 1044 132 11.49 0.32 M 136 11.66 0.32 1220 148 12.17 5.89 5.09 3.60 3.08 2.94 2.53 2.28 2*08 1.80 1.70 1.61 1.54 1.47 1.41 1.36 1*24 1.20 1.17 1.14 um 1.02 1,00 0.982 0.948 0.932 0.887 0,875 0.838 4.42 4.38 4.40 4.40 4.42 4.38 4.40 4.41 4*43 4.40 4.38 4.44 4.42 4.40 4.42 4.42 4.42 4.41 4.42 4.42 4.45 4.41 4.42 4.42 4.40 4.42 4.44 4.44 DUP050150653  ) ' A Pattern Ho. 258B lir-ht yellow Y"'054-D(lot 7634) t PIG. 1 j- DUP050150654 '--u kr*:>>... A. light. yellow Y"2034-D{lot 1137-2-10 . 7:I?.g. 25000 .x FIG. 2. DUP050150655 -13- A Pattsm i?o, 187C Fb3(P0A)2 (369-46Pi) J. n Pattern !To 2000 40/2 FeOv-04 + q % rbgtPOiJg (9G9-46D) FIG. 3 0 Pattern Ho. 222B PbCr04 (969-46A) 0 Pattern Ho. 171C i'bC.r{*C04f.C. : -.i--'t l;t } Ha Stearate DUP050150656 -14- / I PIG* 4 C Pattern No. 304A Ba lithol +`l*lg rosin/mole, boil 2 t o 4 mins (11B7-22B4) D Pattern ITo 399A Rsd 2V r* BON, let Oa. 8^ Sr (1143-14E) DUP050150657 15 > AS 3' Feitem Ho* 3161organic yellow toner '(0,047935) FIG. 5. DUP050150658 is n S. .PIG. 6 D Patten?. 2fo. 249A DC1B - A A -3 s 5 (Cli-iO} o"A (1095'*3ID1) " DUP050150659  17- 1 FIG. 7 D Pattern No 2430 PC 01?A -> AA-in-X (1003-38C1) DUP050150660